Add a field to a model from a custom component field property

In Skuid (most of the time) when I add a rendering condition on a field using a ‘field’ property in a component, skuid will add that field to the model definition.

I want to do something similar in my custom component. I have a field property, and when the user chooses a field I want to make sure it’s in the field property’s model, and if it isn’t, add it.

How would I go about that?